1. Field of the Invention
This invention relates to catheters and specifically to those catheters utilized in electrical pacing or excitation of the heart which require critical placement and firm contact with the inner wall of the heart.
1. Description of the Prior Art
A catheter is a tubular device that is placed within channels, hollow spaces or chambers of the human body. Catheters are generally flexible, hence, maintaining the position of the catheter tip at the desired location for long periods of time is not assured. Various means have been incorporated in the distal tip of catheters to perform fixation. These means include inflatable balloons, suture devices, screw-in connectors and the like. In addition to such mechanical means of fixation, attempts have also been made to employ magnetic means to either directly locate or secure the catheter with respect to the desired location in the body.
Problems concerning such catheters are especially severe for those catheters used in heart pacing and excitation. Failure to maintain critical placement and firm contact of the catheter tip with the inner wall of the heart can result in loss of capture and therefore serious consequences to the operation of the heart of the patient.
Peterson U.S. Pat. No. 3,490,457 is exemplary of a mechanical arrangement for securing a catheter in the bladder or other body cavity. The securing system employs a flexible sleeve which is expandable and retractable. When expanded, the catheter is retained in position and, when retracted, the catheter can be inserted or removed.
Reif, U.S. Pat. No. 3,568,679 mechanically secures a catheter in place by the use of a thin disc of silicon rubber adhesively secured to an external surface of the body. The disc has a locking device which secures the catheter in place externally after it is inserted and reaches the desired position in the body.
Tillander, U.S. Pat. No. 3,674,014 describes a flexible tip catheter which is guided by a magnetic field. A plurality of permanent magnet tubular sections with ball-shaped ends are arranged end to end on the tip of the catheter. This provides the necessary magnetic bendable, flexible tip required to position the catheter.
German Pat. No. 1,261,276 shows use of an external magnet to attract the internal magnet on the distal end of a catheter to a desired point in colonoscopy.
U.S. Pat. No. 2,863,458 to Modny et al. utilizes a magnetic plumb at the end of a nylon line. An external magnet attracts the magnetic plumb, drawing it along the length of a vein, thereby positioning a vein stripper through the vein.
U.S. Pat. No. 3,043,309 to McCarthy discloses an apparatus for performing intestinal intubation and is useful in the procedure called "decompression". A magnet is secured to the tip of an elongated x-ray opaque flexible tube. The tip and tube are then passed through the oesophagus to the stomach of the patient. The stomach is then observed fluoroscopically. A maneuverable magnetic field is then applied to the magnetic material to direct the tip to the pyloric valve in the stomach.
Magnetic fixation of catheters is shown in Moossun's U.S. Pat. No. 3,961,632. There, a trans-abdominal stomach catheter placement system involves a novel magnetic intubation device to distend or advance the forward portion of the stomach wall into relatively close proximity to the exterior abdominal wall.
An article, THE POD AND ITS APPLICATIONS by Frei et al., 1966 Medical Research Engineering pages 11-18, discusses the use of externally driven magnets which are used to control the passage of catheters to a desired location via what the article terms "a pod magnet in a catheter".
The prior art using magnets shown in some of the above patents and the article all involve the use of an external positioning magnet to propel and/or position, or both, the catheter within the body. The application of magnetic means to locating and securing the stimulating electrode of a pacemaker catheter has not been taught or suggested in the prior art.